Facts About Dolphins
Anatomy of a dolphin
Which is the biggest dolphin?
The biggest dolphin is the orca. Even though it is sometimes called a killer whale, it is in fact a member of the dolphin family. Pilot whales are also dolphins!
Which is the smallest dolphin?
In terms of length, the Hectors dolphin and the vaquita (a species of porpoise) are probably the smallest at about 1.4 metres. However, in terms of weight the finless porpoise probably wins as the lightest cetaceans, reaching a maximum weight of 55kg. Approximately 3000 finless porpoises would weigh the same as one blue whale.
How do dolphins sleep?
Unlike you and me, dolphins have to be conscious to decide when to breathe. If they went into a deep sleep they would stop breathing and suffocate or drown. So, their solution is to let only one half of their brain sleep at a time. This way they get the rest they need but stay semi-conscious to continue breathing and look out for any dangers.
How do dolphins drink?
Dolphins don’t need to drink like we do. Their main prey (fish and squid) contains large amounts of water and so dolphins gain water from their food. In addition, dolphins don’t actually need to take in very much fluid because, unlike us, they don’t lose water by sweating.
What do dolphins eat?
This really depends on the species of dolphin and where they live. For example, the bottlenose dolphins living in the Moray Firth, Scotland have different favourite fish depending what time of year it is. In the spring and summer there are big, juicy salmon available for them but in the winter months there are herring and mackerel. So it's a bit like a restaurant having a different menu. Bottlenose dolphins living elsewhere may feed on more tropical species of fish or tuck into an octopus or squid. All dolphins have teeth but they don't chew their food, they just bite and swallow!
Some orcas (killer whales), eat only fish – a favourite being salmon – and others eat much bigger prey including seabirds and mammals such as sea lions. It depends on what food is available to them where they live and what techniques they have learnt to hunt their food.
How long do dolphins live?
In the wild dolphins can live for a long time. Orcas may live for 70 years or more. Bottlenose dolphins can live for at least forty years. Dolphins that are kept in captivity die much earlier than those living in the wild.
Most endangered dolphin
The vaquita, a species of porpoise, which in Spanish means little cow,is only found in a small area of the northern Gulf of California. The worldwide population is estimated to be between 100 and 500 individuals, but most likely around 125.
Maui’s dolphins (a sub-species of the world’s smallest dolphin - the Hectors dolphin) are found off the North Island of New Zealand and have a population currently only numbering approximately 111 individuals. It is also one of the world’s most endangered cetaceans.
The Yangtze River dolphin, also called the baiji, is unfortunately now classed as extinct.
What sounds do dolphins use to communicate?
They use many sounds including clicks, whistles and squeaks.
What is echolocation?
It is the use of sonar to find out where objects are. Dolphins send out sounds and listen to the echo, this tells them exactly what is around them and where their prey is.
The spinner dolphins with their amazing high spinning leap from the water, put on incredible acrobatic displays.
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